Cold cathode ionization vacuum gauges are well known. Three commonly known cold cathode ionization vacuum gauges include normal (noninverted) magnetron type gauges, inverted magnetron type gauges, and Philips (or Penning) gauges. All of these types of gauges have a pair of electrodes (i.e., an anode and a cathode) in an evacuated non-magnetic envelope which is connected to the vacuum to be measured. A high DC voltage potential difference is applied between the anode electrode and the cathode electrode to cause a discharge current to flow therebetween. A magnetic field is applied along the axis of the electrodes in order to help maintain the discharge current at an equilibrium value which is a function of pressure.
Accordingly, a cold cathode ionization vacuum gauge (CCIVG) provides an indirect measurement of vacuum system total pressure by first ionizing gas molecules and atoms inside its vacuum gauge envelope and then measuring the resulting ion current. The measured ion current is directly related to the gas density and gas total pressure inside the gauge envelope, i.e., as the pressure inside the vacuum system decreases, the measured ion current decreases. Gas specific calibration curves provide the ability to calculate total pressures based on ion current measurements.